Tolerance of tetrabenazine during long-term treatment.

Side-effects, haematological, hepatic and renal changes during long-term treatment with tetrabenazine (Nitoman) were assessed in a multicentre trial of 124 patients with various hyperkinetic syndromes. Side-effects were infrequent and usually mild. They necessitated discontinuation of therapy in 5 cases. Changes in clinico-chemical tests during 12 months on tetrabenazine were always minor, nearly always unsystematic and, on the whole, tended more towards a normalization of values than the opposite. Even recognizing the limitations inherent in a uncontrolled trial, we conclude that long-term treatment with tetrabenazine seems to be quite safe.